Process of making projectiles



UNITED STATES PATENT OFFICE.

JOHN L. COX, 0F PHILADELPHIA, PENNSYLVANIA.

PROCESS OF MAKING PROJECTILES.

Specification of Letters Yatent.

Patented Mar. 21, 1922.

No Drawing. Application filed April 21, 1920, Serial No. 375,426. Renewed April 23, 1921. Serial No.

T 0 MN coil-0122 it may com-c2 91.

Be it known that I. Jenn L. Cox, a citizen of the United States, residing at Philadelphia, county of Philadelphia, and State of Pennsylvania, have invented a new and useful Improvement in Processes of Making Projectiles, of which the following is a full, clear, and exact description.

In the manufacture of armor piercing shot and shell, by the process set forth in In pending application for patent, filed July 16, 1919, Serial No. 311,325, I have been able to produce projectiles combining, in a single bloclrof metal, a hard but not brittle head with a relatively soft and very tough body, and which meet the moststringent specifications heretofore imposed by government. Recently, however, projectiles have been subjected to still more severe tests which hitherto none has been able to meet with entire and uniform success. Y'Vhile the penetrating quality of the projectile made in accordance with my said process has been entirely satisfactory, the body of the shell, although softland tough relatively to the point, has still been too brittle to insure the shell against breakage on penetration if fired against an armor plate of calibre thickness at an angle in excess of fifteen degrees from the perpendicular.

The problem, as it presented itself to me, was to reduce the hardness and increase the toughness ofthe main body of the shell while retaining the extreme hardness of the point. In solving the problem, I made certain discoveries that I believe to be new and in any case, in the manufacture of shells, made a novel application of the discovery whereby the results sought were obtained to an unprecedentedly complete degree.

In carrying out my process I prefer to subject the projectile to the same treatment as that set forth in my said application up to and including machining to finished size and the subsequent hardening and drawing in oil, but omitting the last step or series of steps whereby, while the maximum degree of hardness of the point is preserved, the body is given a high degree of toughness and suflicient softness to enable it to be machined for attachment of the band. In other words, my process starts with a projectile which is hard throughout, or with but a little of the base remaining unhardened. It is not necessary, however, that this hard projectile shall have been produced by the process of my said application, as my invention is capable of being applied to a projectile that has been hardened by any process provided it possesses the necessary physical properties.

It is well known that if a piece of steel be heated to a temperature above the critical point, and then cooled suddenly it will harden. In my said application, I pointed out that it was not generally known that sudden cooling from within a limited range below the Ac point as experimentally determined, may produce a distinct degree of hardening and notable loss of toughness, while sudden cooling from a temperature just below this range will impart a degree of toughness superior to that resulting from slow cooling from the same or a somewhat higher temperature. However, even this knowledge, and the process I devised that was in part based thereon, did not suhice to enable me to reduce the hardness to the degree now obtained;

In my present process, I take a projectile that is hard throughout, or hard es sentially throughout, and heat the body (namely, the baseand more or less of the projectile between the base and the point) to a temperature which is within the range, extending from slightly above the Ac point downward, after heating to which the metal would appreciably harden on quenching but would not lose its perfected structure on slow cooling. By the Ac point I mean the Ac point as determined by the instrumen talities ordinarily employed, as by curvedrawing instruments, which point probably only approximates, and does not precisely coincide, with the true Ac or critical point. The downward limit of the range specified may be at times as low as 75 or 100 F., dependent upon the composition of the steel and its physical structure. I prefer to heat the body by immersing it in a bath of lead while maintaining the point unsubmerged.

Instead of quenching I allow the body to cool slowly; that is, slowly relatively to quenching. I prefer to proceed by cooling the body in the air while maintaining the point immersed in cold water, thereby preventing an elevation in temperature in the point during the comparatively slow cooling of the body.

I then reheat the body of the projectile 110 of a single blo to a temperature close to, but below, that from which, if quenched, there -would be any substantial hardening eifect, that is, close to, but below, the range previously specified.

I then quench the whole, or major portion, of the heated part of the projectile and then immerse the point in water.

I thereby produce a projectile having a point of maximum hardness and a body which has so little hardness and brittleness and such exceeding toughness that the shell will resist rupture under the maximum shock contemplated.

Having now fully described my invention, what I claim and desire to protect by Letters Patentis:

1. The process of producing a projectile having superior physical properties, formed of a single block of metal and having a point of a high degree of hardness and a ody of minimum hardness and maximum toughness to resist shock, which comprises heating the body of a hardened projectile to a temperature within the range, extending from slightly above the Ac point downward, after heating to which the metal would appreciably harden on quenching but would not lose its perfected structure on slow cooling; then cooling the body relatively slowly; then reheating the body close to, but below, the said range; and then co0ling suddenly by quenching. r V

2. The process of producing a projectile having superior ghysical properties, formed 0 of metal and having a point of a high degree of hardness and a body of minimum hardness and maximum toughness to resist shock, which comprises heating the body of a hardened projectile to a temperature within a range, extending from slightly above the A0 point clownward, within which the metal would appreciably harden on quenching but would not lose its perfected structure on slow cooling, without subjecting the point of the projectile to reheating except to the relatively low degree produced by conduction; then c0oling the body in air while the point is immersed in water; then reheating the body close to, but below, the said range; and then cooling suddenly by quenching.

3. The process of producing a projectile having superior physical properties, formed oi. a single block of -metal and having a pointof ahigh degree ofhardness and abody of minimum hardness and maximum toughness to resist shock, which comprises hardening the projectile, heating only the body of the projectile to a temperature within a range, extending from slightly above the'Ac point downward, within which the metal would appreciably harden on quenching but would not lose its perfected structure on slow cooling; then cooling the body relatively slowly; then reheating the body close to, but below, the said range; and then cooling suddenly by quenching.

In testimony of which invention, I have hereunto set my hand, at Philadelphia, Pa.. on this 13th day of April, 1920. a.

v r JOHN L. COX. 

